Telescope Reviews: Fork mounts and AP

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Equipment Discussions >> Mounts

Pages: 1

jerry32
member

Reged: 10/30/10

Fork mounts and AP
#5608312 - 01/06/13 12:57 PM

are fork mounts any good for AP?? just wondering.

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neotesla
Pooh-Bah

Reged: 11/18/10

Loc: Canada

Re: Fork mounts and AP new

[Re: jerry32]
#5608330 - 01/06/13 01:03 PM

You will need a field derotator or a wedge to make it work...

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Cliff Hipsher
scholastic sledgehammer

Reged: 12/31/08

Loc: North Chesterfield, VA

Re: Fork mounts and AP new

[Re: jerry32]
#5608388 - 01/06/13 01:34 PM

Sure.

As long as you do a proper polar alignment and the mount tracks accurately.

I started out imaging the planets using a Meade 2080 LX5 on a wedge. Worked just fine.

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Startraffic
sage

Reged: 02/12/06

Loc: Lat. 39.143345, Long. -77.1748...

Re: Fork mounts and AP new

[Re: jerry32]
#5610402 - 01/07/13 03:07 PM

Jerry,
Yes, they can be you'll need either a field de-rotator or a wedge to put the base at an angle equal to your latitude. I believe that the de-rotator is the more $$$ way to go, ut could be wrong.

Clear Dark Skies
Startraffic
39.138274 -77.168898

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David Pavlich
Transmographied

Reged: 05/18/05

Loc: Mandeville, LA USA

Re: Fork mounts and AP new

[Re: jerry32]
#5610643 - 01/07/13 06:05 PM

Or you could give the ole' credit card a workout.

David

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neotesla
Pooh-Bah

Reged: 11/18/10

Loc: Canada

Re: Fork mounts and AP new

[Re: David Pavlich]
#5610644 - 01/07/13 06:08 PM

Quote:

Or you could give the ole' credit card a workout.

David

Makes these seem cheap...

http://trackthestars.com/

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MrJones
Pooh-Bah

Reged: 09/15/10

Loc: Indiana

Re: Fork mounts and AP new

[Re: neotesla]
#5610659 - 01/07/13 06:19 PM

Basically up to 30s exposures can be done without a wedge. Stacking programs like Deep Sky Stacker can compensate for the rotation between exposures.

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Starhawk
Post Laureate

Reged: 09/16/08

Loc: Tucson, Arizona

Re: Fork mounts and AP new

[Re: MrJones]
#5611890 - 01/08/13 12:44 PM

The wedge really is the way to go. If you don't have one, the rotation solution for every single frame is different from every other frame.

So if your reference frame is 0, then the next one may need to be rotated .02 degrees, the one after that .04 degrees, the one after that got blurred so it was tossed out, the next one is .08, the one after that had to be tossed, the next is .12, and so on.

To say it is tedious is an understatement. And this has to be corrected before you can give them to an image stacker capable of auto-alignment.

The mounts behave quite well on a wedge, though they are quite heavy. For a C8 sized scope, the forks and base are 2/3 of the weight of what you have to move.

So, while they are usable, deforking is far more portable, and allows you to use the better mounts.

-Rich

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rmollise
Postmaster

Reged: 07/06/07

Re: Fork mounts and AP new

[Re: Starhawk]
#5611927 - 01/08/13 01:13 PM

Quote:

So if your reference frame is 0, then the next one may need to be rotated .02 degrees, the one after that .04 degrees, the one after that got blurred so it was tossed out, the next one is .08, the one after that had to be tossed, the next is .12, and so on.

To say it is tedious is an understatement. And this has to be corrected before you can give them to an image stacker capable of auto-alignment.

This is really not much of a problem with most software. The problem? You can stack as many subs as you want, but you are always limited to sub-frame exposures that show minimum trailing due to field rotation. You might get away with a minute in some areas of the sky, but a longer exposure than that is really much, much better.

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Starhawk
Post Laureate

Reged: 09/16/08

Loc: Tucson, Arizona

Re: Fork mounts and AP new

[Re: rmollise]
#5613352 - 01/09/13 09:15 AM

Well, yeah, but you can't take longer exposures in alt-az. That's why it's rotational heck. I have seen a lot of software claim it could do rotation automatically. I've never seen anything resembling a successfully rotated stack run in front of me. Auto-align, yes. Rotate- not even close.

-Rich

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rmollise
Postmaster

Reged: 07/06/07

Re: Fork mounts and AP new

[Re: Starhawk]
#5613379 - 01/09/13 09:25 AM

Quote:

Well, yeah, but you can't take longer exposures in alt-az. That's why it's rotational heck. I have seen a lot of software claim it could do rotation automatically. I've never seen anything resembling a successfully rotated stack run in front of me. Auto-align, yes. Rotate- not even close.

-Rich

Which is just what I said--or thought it was, anyhow.

As far as rotation, I have never, ever had a problem with Nebulosity correctly rotating frames. Granted, they weren't terribly rotated to begin with, but I am not a drift-aligner.

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Starhawk
Post Laureate

Reged: 09/16/08

Loc: Tucson, Arizona

Re: Fork mounts and AP new

[Re: rmollise]
#5613405 - 01/09/13 09:38 AM

I think that's the core issue, Rod. The amount of rotational error in even a lousy polar alignment is small. It varies across the sky for alt-az, and is worst in the sweet spot near the zenith, and pretty bad anywhere near the celestial equator.

So, I got into doing precision polar alignments and have enjoyed seeing frames stack like playing cards.

I've kept my deforked Nexstar GPS mounts and am nearly finished with an all-metal conversion of my Nexstar 8 forks into a small scope mount- which I expect to work quite well at focal lengths up to 1000mm, since it was pretty good at the C8's focal length. It is quite easy to move without a bulky and fragile OTA attached.

-Rich

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MrJones
Pooh-Bah

Reged: 09/15/10

Loc: Indiana

Re: Fork mounts and AP new

[Re: Starhawk]
#5613447 - 01/09/13 10:19 AM Attachment (11 downloads)

I don't disagree with the above, but for someone that just wants to try AP and have an easy to use visual scope that can see things at the azimuth

driven alt-az mounts might be the better solution. Here's a quick Leo triplet from my LT6 with not that many 30s subs.

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rmollise
Postmaster

Reged: 07/06/07

Re: Fork mounts and AP new

[Re: MrJones]
#5613548 - 01/09/13 11:38 AM

Certainly I agree that if you want to start imaging and are set up for alt-az, give it a try. The results may surprise. That is a very nice picture, dude.

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